Former Washington Post Ombudsman Michael Getler, writing in Democracy: A Journal of Ideas:
The [New York] Times actually published some stories, most notably a piece by Michael Gordon and Judith Miller on September 8, 2002, that wound up contributing to what turned out to be the administration's bogus case for war. The [Washington] Post was much less guilty of that particular sin, but it displayed a pattern of missing or downplaying events that unfolded in public-events that might have played a role in public opinion during the run-up to the war.
Some examples: In the summer and fall of 2002, the paper failed to record promptly the doubts of then-House Majority Leader Dick Armey. When Brent Scowcroft, the national security adviser to George H.W. Bush, wrote a cautionary op-ed in The Wall Street Journal, it apparently didn't strike anyone at the Post as news. ...The testimony of three retired four-star generals warning against an attack before the Senate Armed Services Committee was not covered at all. Speeches by Senator Ted Kennedy and Senator Robert Byrd that seem prescient today were not covered.
The list goes on. Large anti-war rallies in London and Rome went unreported the day after. In October, when more than 100,000 gathered in Washington to protest the war, the story went in the Metro section because the Post underestimated its size.
Then there was the Page A18 problem. The Post, to be sure, did put some good stories challenging the official line on the front page. But they consistently seemed to be outnumbered by important stories, usually sourced to anonymous government or military insiders, that were positioned way inside the newspaper.
Here's a brief sampling of additional Post headlines that, rather stunningly, failed to make the front of the newspaper: “Observers: Evidence for War Lacking,” “U.N. Finds No Proof of Nuclear Program,” “Bin Laden-Hussein Link Hazy,” “U.S. Lacks Specifics on Banned Arms,” “Legality of War Is a Matter of Debate,” and “Bush Clings to Dubious Allegations About Iraq.” In short, it wasn't the case that important, challenging reporting wasn't done. It just wasn't highlighted.
Apologies for the lengthy excerpt, but there's much, much more that is well worth reading.